To create a clinically relevant vector for vascular-based diseases, we must advance three pivotal efforts. First, it is critical to formally correct an established disease phenotype via systemic administration of a vector that de-targets the liver and thus reduces adenovirus (Ad) associated liver toxicity. Second, development of a safer, less immunogenic Ad vector capable of long-term gene expression will be required to realize human clinical translation of a gene therapy for diseases involving endothelium. To this end, we will combine our current targeting technology with "gutless" Ad vectors, known to provide long-term gene expression in vivo as a result of their reduced immunogenicity. Finally, to further increase the clinical utility of our vector, we propose the development of a single component targeted Ad vector compatible with large scale production and FDA approval. In this regard, we have recently developed the methodology to incorporate functional single chain antibody (scFv) targeting moieties into the Ad capsid resulting in highly selective gene delivery to specific cell surface markers. This key technological development will allow us to extend our established targeting paradigm to a single component vector with genetically incorporated targeting. We hypothesize that the combination of these technologies will allow the realization of a clinically relevant gene therapy vector for diseases requiring systemic injection and significant pulmonary endothelium involvement. Our specific aims are thus: Specific Aim 1: To evaluate the ability of double-targeted Ad vectors to correct disease involving the pulmonary endothelium. Specific Aim 2: To create targeted gutless Ad vectors capable of long term gene expression in the pulmonary endothelium. Specific Aim 3: To create a single-component, targeted gutless Ad employing genetically incorporated recombinant antibodies to target the pulmonary endothelium. The successful completion of these specific aims will provide important and timely data regarding the efficacy of endothelial targeted gene therapy and lay the groundwork for other endothelial based diseases. Further, our studies will clearly establish therapeutic gain associated with decreased vector immunogenicity and long term gene expression. Finally, the studies proposed herein will provide a critical step toward a safer, single component vector compatible with large-scale production and clinical translation. PUBLIC HEALTH RELEVANCE: Adenovirus (Ad) based vectors are widely used in clinical trials due to their well characterized biology and positive safety profile. However, the majority of clinical applications employing Ad based vectors utilize local administration due to limitations associated with first generation Ad vectors. In this proposal, we seek to engineer a safer, less immunogenic Ad vector capable of long-term gene expression.